add functional tests for defininig and using ES modules

Author: Gubaer

build.gradle

@@ -291,6 +291,7 @@ tasks.register('testWithGraalVMJDK', Test) {
     include "org/openstreetmap/josm/plugins/scripting/graalvm/esmodule/*.class"
     include "org/openstreetmap/josm/plugins/scripting/graalvm/*.class"
     exclude "org/openstreetmap/josm/plugins/scripting/graalvm/GraalVMNotPresentTest.class"
+    include "org/openstreetmap/josm/plugins/scripting/esmodules/ESModuleUsageTest.class"
     testLogging {
         events TestLogEvent.FAILED, TestLogEvent.PASSED
         exceptionFormat = TestExceptionFormat.FULL

src/test/functional/groovy/org/openstreetmap/josm/plugins/scripting/esmodules/ESModuleUsageTest.groovy

@@ -0,0 +1,45 @@
+package org.openstreetmap.josm.plugins.scripting.esmodules
+
+import org.graalvm.polyglot.Context
+import org.graalvm.polyglot.HostAccess
+import org.graalvm.polyglot.Source
+import org.junit.jupiter.api.Test
+import org.openstreetmap.josm.plugins.scripting.JOSMFixtureBasedTest
+import org.openstreetmap.josm.plugins.scripting.graalvm.GraalVMFacade
+import org.openstreetmap.josm.plugins.scripting.graalvm.esmodule.ESModuleResolver
+import org.openstreetmap.josm.plugins.scripting.graalvm.esmodule.FileSystemESModuleRepository
+
+import static org.junit.Assert.assertEquals
+
+class ESModuleUsageTest extends JOSMFixtureBasedTest {
+
+    static private def buildSource(String source) {
+        return Source.newBuilder("js", source, null)
+            .mimeType("application/javascript+module")
+            .build()
+    }
+
+    @Test
+    void "should successfully import and use a function provided by 'module-a' in the file system"() {
+        final resolver = ESModuleResolver.instance
+        final repo = new FileSystemESModuleRepository(new File(
+            getProjectHome(),
+            "src/test/resources/sample-modules/module-a"
+        ))
+        resolver.setUserDefinedRepositories(List.of(repo))
+
+        final script= """
+        import {add} from 'module-a'
+        add(1,1)
+        """
+        def context = Context.newBuilder("js")
+            .allowHostAccess(HostAccess.ALL)
+            .allowHostClassLookup(className -> true)
+            .allowIO(true)
+            .fileSystem(resolver)
+            .build()
+        GraalVMFacade.populateContext(context)
+        final result = context.eval(buildSource(script))
+        assertEquals(2, result.asInt())
+    }
+}

src/test/resources/sample-modules/.gitignore

@@ -0,0 +1 @@
+!sample-modules.jar

src/test/resources/sample-modules/Makefile

@@ -0,0 +1,4 @@
+sample-modules.jar:
+	jar cf sample-modules.jar \
+		README.md \
+		module-a 

src/test/resources/sample-modules/README.md

@@ -0,0 +1,21 @@
+A collection of sample ECMAScript modules.
+
+These ES modules are used as test cases. Some of them are very basic and export just a simple function provided in a single source file. Others have richer internal structure, internally import and use sub modules, or even import functions from other modules in this collection.
+
+# How to use?
+
+They are useful for two purposes:
+
+1. as test case in **automatized functional tests**
+
+    Test scripts import them and use the exported functions. The main goal is to test whether `import` statements are correctly resolved.
+    See [ESModuleUsageTest.groovy](../../../test/functional/groovy/org/openstreetmap/josm/plugins/scripting/esmodules/ESModuleTest.groovy) for an example.
+
+2. as test case in **manual interactive tests**
+
+    To test the scripting plugin interactively in a running JOSM process the modules can be used as test modules. 
+
+    In order to use them, you first have to configure an ES module repository in the scripting plugin preferences.
+    1. Select menu item *Scripting -> Settings ...*
+    2. Select the tab **ES Modules**
+    3. Add a new repository pointing this directory

src/test/resources/sample-modules/module-a/module-a.mjs

@@ -0,0 +1,14 @@
+/*
+ * Module 'module-a' exports a single function 'add'.
+ *
+ * Here's a sample script using the module
+ * <pre>
+ * import {add} from 'module-a'
+ * import * as console from 'josm/scriptingconsole'
+ * const b = add(1,1)
+ * console.println(`result: ${b}`)
+ * </pre>
+ */
+export function add(a, b) {
+    return a + b
+}